Beginner warning: Details follow which you may not wish to read at your current level.

We only see this spell used once. Hermione, having seen Ron and Lavender locked in one of their embraces, has retreated to a disused classroom, where she has moodily created a flock of canaries which are circling her. Ron and Lavender, apparently seeking some privacy, also enter the classroom; Lavender quickly backs out, but Ron stays to exchange some words with Hermione. Hermione, angered, uses the spell to set the canaries on Ron as she is leaving.

There is mention later that Ron still bears the scars of the canary beaks and talons.

It is uncertain whether this spell would work on any creature, or only on creatures that the caster has created. As we see this spell only the one time, we can only guess at its effects and applicability.